An apparatus for recognizing a running route or lane area according to image information obtained through an image pickup operation by an onboard camera has been described, for example, in the JP-A-4-134503 (article (1)).
The apparatus above includes scan means for extracting a running route edge from image information inputted via image input means and scanning upward an image associated with the extracted running route edge beginning at a particular reference point in a horizontal direction and means for setting a center of the scanned area to a particular reference point in the horizontal direction for the subsequent scanning operation such that the running route zone according to the area scanned by the scan means.
In other words, a color corresponding to pixels which constitute the image information and which are at the lower portion of the screen is assumed as a particular color (color of the road surface) to examine an area including a set of pixels having color information equivalent to the particular color, thereby determining a zone or an area enclosed with the particular color as a road area in front of the vehicle.
However, in accordance with the prior art described in article (1), although the zone enclosed with the particular color is assumed as a road area in front of the vehicle, there still remains a problem, for example, occurrence of an event in which the road zone enclosed with road edges (corresponding to lines of the vehicle) cannot be exactly extracted only by the technology.
For example, in a case in which the contour of the road area in front of the vehicle is complicated due to presence of wheel tracks, it is determined that there exist edges of the running route in addition to the line in the road. Resultantly, the edge cannot be appropriately recognized. In addition, there have frequently occurred a case in which the road zone cannot be correctly recognized.
On the other hand, for such a vehicle which runs on a road, it is necessary for the driver to appropriately drive the vehicle so that the vehicle runs along a predetermined running lane.
Consequently, the driver is required to continuously monitor the running road surface to pay attention to the state of the road surface and presence of other vehicles and obstacles. Therefore, a heavy psychological and physical load is imposed on the driver.
As a result, if the driver loses concentration or the driver's attention is distracted in a driving state in which the vehicle exceeds its own running lane at random, there may possibly occur a grave accident.
In particular, on a general road including opposing traffic lanes in which vehicles run mutually in the opposite directions, if a vehicle exceeds a central line of the road into the opposing traffic lane, there will possibly occur quite a serious accident.
To solve the problem, the JP-A-62-221800 (article (2)) has disclosed an apparatus in which an image of a road surface in front of the pertinent vehicle is obtained by a color image pickup device. According to the obtained color image signal, a line of the vehicle is decided according to the difference in color between the line and the road surface to thereby issue an alarm message to the driver of the vehicle.
In the conventional technology described in article (2), the existence of the line is determined according to a color representing the line, namely, yellow or white.
Since the road surface is grey and hence it is guaranteed to discriminate the road surface from the yellow line. However, the discrimination is impossible by the color difference between the white line and the grey road surface and it is therefore necessary to achieve the discrimination according to luminance.
Consequently, in a case in which the state around the road, namely, the road environment is altered, for example, luminance varies in a tunnel (an obtained image is yellow due to the yellow illumination) or due to illumination at night, it is difficult to recognize the line of vehicle according to the change in the state.
On the other hand, in the apparatus in which the line of vehicle is recognized according to image data obtained by the onboard camera, there has been generally used a method in which the state in front of the vehicle is shot by one camera. However, such an apparatus is attended with the following problems. To recognize the state in a wide range, when there is disposed a wide-angle lens, it is difficult to recognize the line in the faraway place. On the other hand, to recognize the line in the faraway place, when there is adopted a zoom mechanism of the optical system, the recognizable field of vision is restricted.
To improve the apparatus, there has been disclosed an apparatus described, for example, in the JP-A-06-229760 (article (3)).
The apparatus includes a solid-state image pickup block including an optical system having a low zoom rate and a solid-state image pickup block including an optical system having a high zoom rate. Comparing image data attained by the block of low zoom rate with that obtained by the block of high zoom rate, it is recognized that the running route in a relatively faraway place in front of the vehicle has a contour of a curved route or that the vehicle is in a state to enter a curved route.
However, according to the prior art of article (3) described above, the configuration includes a solid-state image pickup block including an optical system having a high zoom rate to recognize the contour of the line in a relatively faraway place. Therefore, there are required two optical systems for the high and low zoom rates and two solid-state image pickup blocks for the respective optical systems. This leads to a problem, namely, the size of the apparatus is increased and hence the apparatus is not necessarily suitable as a device to be mounted on a vehicle; moreover, the production cost thereof is inevitably soared.
Additionally, in consideration of the environment related to the mounting of the apparatus, namely, in the environment of a high temperature and a large amplitude of vibration, it is strongly desired that the number of optical systems is to be possibly reduced in the configuration of the apparatus.
It is therefore a first object of the present invention in relation to the problem of the prior art of article (1) to provide an apparatus in which when recognizing a line of vehicle for a running lane of the vehicle according to image information obtained by a camera mounted thereon, the line of vehicle can be correctly recognized even there exists such an edge other than the line as a noise in the road area in front of the vehicle.
A second object of the present invention in relation to the problem of the prior art of article (2) is to provide a road surface monitor apparatus employing an image process in which changes in luminance and color of the road surface just in front of the vehicle are determined to discriminate the road surface from the line of vehicle according to the luminance and color, thereby appropriately recognizing the line.
A third object of the present invention in relation to the problem of the prior art of article (3) is to provide a road surface monitor apparatus employing an image process in which when recognizing a line of vehicle for a running lane of the vehicle according to image information obtained by a camera mounted thereon, the configuration of the apparatus is not required to include a plurality of optical systems and the line can be correctly recognized in a running lane in a relatively faraway place while retaining a wide field of vision.